Today, we’re going to explore conditional logic in Ruby using the Pagan Wheel of the Year. The Wheel of the Year is a set of eight holidays adopted by many Pagan traditions, and each holiday observes the changing of the seasons.
This witch likes to party. Just kidding, I’m basically a recluse.
However, I do like to know when the next holiday is coming up so I can observe it privately or with a few friends. So today, our goal is to write a method that, given a degree of latitude and date, will return the upcoming Pagan holiday. To accomplish this, we will use if statements, the ternary operator, and case statements.
Basic Setup
Before we can get into the conditional logic of our program, we need to do some basic setup. First, we’ll require the date gem, which allows our program to use the Date class. We’ll also get some input from the user to store their location.
Determine the Hemisphere
Because the Wheel of the Year is an observation of the seasons, the holidays differ based on one’s location on the globe. For example, when the Northern hemisphere celebrates the winter solstice (Yule), the Southern hemisphere is celebrating the summer solstice (Litha).
We’ll use an if statement in our #hemisphere method. Let’s quickly look at the basic syntax:
if condition is met
execute this code
end
We can also add an else to our statement:
if condition is met
execute this code
else
execute this code
end
If we need more than two options, the elsif comes in handy:
if condition is met
execute this code
elsif this condition is met
execute this code
else
execute this code
end
Back to our program:
Write the Holiday Methods
Now, we need to write two methods, #northern and #southern, which, when given a date, return the upcoming holiday. The logic for these two methods is the same, but the holidays are shifted by 6 months. To keep this brief, we’ll only talk through the #northern method.
Before we launch into the code, let’s talk about case statements and ternary operators. Both of these are used to simplify if statements.
Ternary Operator
The ternary operator is used to write simple, one-line if statements. The syntax looks like this:
# condition ? return-this-if-true : return-this-if-false
# Here’s a quick example:
3 > 5 ? '3 is greater than 5' : '3 is less than 5'
# Returns ‘3 is less than 5’
Case Statements
case statements are used to simplify really long if statements. When your if statement has three or more elsif's, consider switching to a case statement. Let’s look at the syntax:
# case condition
# when result-1
# return this code
# when result-2
# return this code
# when result-3
# return this code
# when result-4
# return this code
# when result-5
# return this code
# else
# return this code
# end
# Quick example:
x = 5
case x
when 1
"x is 1"
when 2
"x is 2"
when 3
"x is 3"
when 4
"x is 4"
when 5
"x is 5"
else
"x doesn’t match"
end
# Returns ‘x is 5’
Returning to our Wheel of the Year, let’s write those methods:
Find the Next Holiday
We’ve just got one more method to bring it all together. This one is for all the marbles:
Success!
We did it! Now we’ll always know what the next Pagan holiday is. Next time someone asks you if you understand conditional logic, just channel Endora:
You are a code witch! Of course you do!